add support for changing which back camera is being used

iOS/GBViewController.m

@@ -52,6 +52,10 @@
     NSTimer *_disableCameraTimer;
     AVCaptureDevicePosition _cameraPosition;
     UIButton *_cameraPositionButton;
+    NSArray *_allCaptureDevices;
+    NSArray *_backCaptureDevices;
+    AVCaptureDevice *_selectedCaptureDevice;
+    UIButton *_changeCameraButton;
     
     __weak GCController *_lastController;
     
@@ -241,30 +245,82 @@ static void rumbleCallback(GB_gameboy_t *gb, double amp)
     
     _motionManager = [[CMMotionManager alloc] init];
     _cameraPosition = AVCaptureDevicePositionBack;
+    _selectedCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType: AVMediaTypeVideo];
+
+    // Back camera setup
+    NSArray *deviceTypes = @[AVCaptureDeviceTypeBuiltInWideAngleCamera,
+                             AVCaptureDeviceTypeBuiltInTelephotoCamera];
+    if (@available(iOS 13.0, *)) {
+        // AVCaptureDeviceTypeBuiltInUltraWideCamera is only available in iOS 13+
+        deviceTypes = @[AVCaptureDeviceTypeBuiltInWideAngleCamera,
+                       AVCaptureDeviceTypeBuiltInUltraWideCamera,
+                       AVCaptureDeviceTypeBuiltInTelephotoCamera];
+    }
+
+    // Use a discovery session to gather the capture devices (all back cameras as well as the front camera)
+    AVCaptureDeviceDiscoverySession *cameraDiscoverySession = [AVCaptureDeviceDiscoverySession
+                                                                    discoverySessionWithDeviceTypes:deviceTypes
+                                                                    mediaType:AVMediaTypeVideo
+                                                                    position:AVCaptureDevicePositionUnspecified];
+    _allCaptureDevices = cameraDiscoverySession.devices;
+
+    // Filter only the back cameras into a list used for switching between them
+    NSMutableArray *filteredBackCameras = [NSMutableArray array];
+    for (AVCaptureDevice *device in _allCaptureDevices) {
+        if ([device position] == AVCaptureDevicePositionBack) {
+            [filteredBackCameras addObject:device];
+        }
+    }
+    _backCaptureDevices = filteredBackCameras;
+
     _cameraPositionButton = [[UIButton alloc] initWithFrame:CGRectMake(8,
                                                                        0,
                                                                        32,
                                                                        32)];
+    _changeCameraButton = [[UIButton alloc] initWithFrame:CGRectMake(8,
+                                                                     0,
+                                                                     32,
+                                                                     32)];
     [self didRotateFromInterfaceOrientation:[UIApplication sharedApplication].statusBarOrientation];
     if (@available(iOS 13.0, *)) {
         [_cameraPositionButton  setImage:[UIImage systemImageNamed:@"camera.rotate"
                                                  withConfiguration:[UIImageSymbolConfiguration configurationWithScale:UIImageSymbolScaleLarge]]
                                 forState:UIControlStateNormal];
         _cameraPositionButton.backgroundColor = [UIColor systemBackgroundColor];
+
+        [_changeCameraButton  setImage:[UIImage systemImageNamed:@"camera"
+                                                withConfiguration:[UIImageSymbolConfiguration configurationWithScale:UIImageSymbolScaleLarge]]
+                                forState:UIControlStateNormal];
+        _changeCameraButton.backgroundColor = [UIColor systemBackgroundColor];
     }
     else {
-        UIImage *image = [[UIImage imageNamed:@"CameraRotateTemplate"] imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
-        [_cameraPositionButton  setImage:image
+        UIImage *rotateImage = [[UIImage imageNamed:@"CameraRotateTemplate"] imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
+        [_cameraPositionButton  setImage:rotateImage
                                 forState:UIControlStateNormal];
         _cameraPositionButton.backgroundColor = [UIColor whiteColor];
+
+        UIImage *selectCameraImage = [[UIImage imageNamed:@"CameraTemplate"] imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
+        [_changeCameraButton  setImage:selectCameraImage
+                                forState:UIControlStateNormal];
+        _changeCameraButton.backgroundColor = [UIColor whiteColor];
     }
     _cameraPositionButton.layer.cornerRadius = 6;
     _cameraPositionButton.alpha = 0;
     [_cameraPositionButton addTarget:self
                               action:@selector(rotateCamera)
                     forControlEvents:UIControlEventTouchUpInside];
+    _changeCameraButton.layer.cornerRadius = 6;
+    _changeCameraButton.alpha = 0;
+    [_changeCameraButton addTarget:self
+                              action:@selector(changeCamera)
+                    forControlEvents:UIControlEventTouchUpInside];
+
     [_backgroundView addSubview:_cameraPositionButton];
-    
+    // Only show the select camera button if we have more than one back camera to swap between.
+    if ([_backCaptureDevices count] > 1) {
+        [_backgroundView addSubview:_changeCameraButton];
+    }
+
     _cameraQueue = dispatch_queue_create("SameBoy Camera Queue", NULL);
     
     [UNUserNotificationCenter currentNotificationCenter].delegate = self;
@@ -686,6 +742,7 @@ static void rumbleCallback(GB_gameboy_t *gb, double amp)
 {
     UIEdgeInsets insets = self.window.safeAreaInsets;
     _cameraPositionButton.frame = CGRectMake(insets.left + 8, _backgroundView.bounds.size.height - 8 - insets.bottom - 32, 32, 32);
+    _changeCameraButton.frame = CGRectMake(insets.right - 8, _backgroundView.bounds.size.height - 8 - insets.bottom - 32, 32, 32);
 }
 
 - (UIInterfaceOrientationMask)supportedInterfaceOrientations
@@ -1123,12 +1180,20 @@ didReceiveNotificationResponse:(UNNotificationResponse *)response
 
 - (AVCaptureDevice *)captureDevice
 {
-    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
-    for (AVCaptureDevice *device in devices) {
+    for (AVCaptureDevice *device in _allCaptureDevices) {
         if ([device position] == _cameraPosition) {
-            return device;
+            // There is only one front camera, return it
+            if (_cameraPosition == AVCaptureDevicePositionFront) {
+                return device;
+            }
+
+            // There may be several back cameras, return the one with the matching type
+            if ([device deviceType] == [_selectedCaptureDevice deviceType]) {
+                return device;
+            }
         }
     }
+    // Return the default camera
     return [AVCaptureDevice defaultDeviceWithMediaType: AVMediaTypeVideo];
 }
 
@@ -1292,4 +1357,23 @@ didReceiveNotificationResponse:(UNNotificationResponse *)response
     });
 }
 
+- (void)changeCamera
+{
+    dispatch_async(_cameraQueue, ^{
+        // Get index of selected camera and select the next one, wrapping to the beginning
+        NSUInteger i = [_backCaptureDevices indexOfObject:_selectedCaptureDevice];
+        int nextIndex = (i + 1) % _backCaptureDevices.count;
+        _selectedCaptureDevice = _backCaptureDevices[nextIndex];
+
+        [_cameraSession stopRunning];
+        _cameraSession = nil;
+        _cameraConnection = nil;
+        _cameraOutput = nil;
+        if (_cameraNeedsUpdate) {
+            _cameraNeedsUpdate = false;
+            GB_camera_updated(&_gb);
+        }
+    });
+}
+
 @end